WATERSHED RESTORATION
<br />with ahigh-resilience capacity are improving or have been
<br />restored should restoration efforts focus on areas that have
<br />generally lost the capability of natural recovery, even after
<br />the cessation of human perturbations. However, special
<br />situations may exist in which degraded habitats of species
<br />near extinction can only be restored at high risk and cost;
<br />such areas assume a high priority for improvement.
<br />Where possible, managers should emphasize preservation
<br />because preservation of intact ecosystems is typically less
<br />expensive than restoring degraded systems (Cairns 1993).
<br />Intact ecosystems are not only valuable sources of biologi-
<br />cal diversity, but they also provide important reference
<br />sites that land managers may seek to emulate in their
<br />restoration activities. Rather than referring to a handbook,
<br />]and managers should obtain the "blueprints" for the ulti-
<br />mate outcomes of planned restoration activities in adjacent
<br />sites from intact streams. Because the failure rate of restor-
<br />ing degraded ecosystems is far greater than that of simply
<br />protecting fully functional sites, protecting and preserving
<br />intact ecosystems should represent the first priority of any
<br />watershed-scale restoration plan.
<br />At the other extreme, many areas exist where ecological
<br />restoration in the strictest sense is neither economically,
<br />socially, nor technologically feasible (e.g., metropolitan
<br />__
<br />..Reviews of ~instream habitat --
<br />management-projects throughout the
<br />western United States clearly indicate
<br />that passive restoration has been
<br />the critical first step in successful
<br />riparian restoration` programs.
<br />reaches, dredged mine sites, etc.). If restoration practices
<br />are pursued in these situations, they may be costly. How-
<br />ever, stream enhancement activities should not be ruled
<br />out in these scenarios, particularly if such acti~-ities would
<br />diminish harm to dot~-nstream or upstream riparian and
<br />aquatic ecosystems.
<br />Thy domain of riparian and stream restoration lies
<br />bet~~•een these t~-~ o extremes (Figure 2). A successftl ri~ari-
<br />-._~. restoraro. program ~~~ill result in the pemetuation of
<br />`~~Ces~cs t;',at c'ietermine eCO~ysteil strLICLLlrv', illnCtlOn,
<br />and eyoiutionar~~ trajector,~. Ho;~ e~.~er, this operating prin-
<br />ciple is stated ~~•ith the recognition that the intact ~~-i1d-
<br />lands of today and the future will exist in a fragmented
<br />landscape and will require specific preservation manage-
<br />ment activities such as prescribed fires, suppression of
<br />arson fires, control of biotic invasions, and maintenance of
<br />natural hydrologic disturbance regimes.
<br />After identifying those degraded sites where restoration
<br />is deemed feasible, scientists must determine the causes of
<br />degradation and the activities preventing recovery (Besch-
<br />ta 1997). Also important is the identification of biotic
<br />components of the ecosystem that have been extirpated
<br />and the presence of biotic invaders that may prevent recoy-
<br />er~-. I~~ addition to biotic considerations, c~(enri;~; must
<br />Fps _ ~-~
<br />determine the degree to which the hydrologic and geo-
<br />morphic features of the ecosystem have been (or are being
<br />altered. This includes determining the influences of past
<br />management activities on channel morphology, channel
<br />incision, hyporheic flows, water table dynamics, and Ovate
<br />quality (i.e., the linkages between the terrestrial and aquat-
<br />ic system). From this initial analysis, not only can the ex-
<br />tent and causes of ecosystem degradation be addressed, brit
<br />potential restoration options may become evident. Obviously,
<br />even at this stage, restoration is a multidisciplinary effort.
<br />The desired endpoints of restoration efforts are naturally
<br />dynamic and self-sustaining ecosystems (Figure 2). Given
<br />the fluctuating nature of environmental factors inherent to
<br />all natural systems, restoration managers should empha-
<br />size ecosystem processes and function rather than some
<br />preconceived landscape form. Fisheries professionals should
<br />recognize that because of the likely permanence of many
<br />exotic species, extinctions of native species, long-term
<br />changes in soil productivity due to erosion, and other severe
<br />environmental perturbations, complete recovery may not
<br />always be possible. In such cases, goals of restoration are
<br />to return a riparian system to a "potential natural commu-
<br />nity;" whereby the ecosystem is nahirally functioning in a
<br />manner as closely as possible to that in which it evolved.
<br />Passive Restora#ioti
<br />Once professionals have decided where to implement
<br />restoration activities, the first and most critical step is to
<br />halt activities causing degradation or preventing recovery,
<br />an approach referred to as yassiz~e or natural restoration
<br />(Kauffman et al. 1993; Kauffman et al. 1995). Many ripari-
<br />an zones are capable of rapid recovery after human per-
<br />turbations stop because the biota has evolved adaptations
<br />to survive and even reproduce despite frequent natural
<br />disturbance events characteristic of riverine systems
<br />(Barnes 1953; <'Nilson 1970; Gecy and Wilson 1990).
<br />In western riparian zones the taco most common exam
<br />pies of successful passive ecological restoration-are the
<br />rewatering of streams after years of ~rithdrawal for a~ri-
<br />cultural or municipal purposes and the cessation of li~-e-
<br />stock grazing in riparian areas. Stream fio~~• diyersirn~.,
<br />combined ~+,•itii hea~-y li~-estock gazing, can resu1~ in serer,
<br />degradation of riparian and stream ecosystems. ~~it~ the
<br />return of perennial instream tio~~-s and the halt of li~~esto; b.
<br />,razing, the recovery of riparian vegetation can be dra-
<br />matic. For example, in the ;Mono basin of California, 215
<br />of the area of riparian vegetation lost during a 50-vr peri-
<br />od of water diversion (1910-1989) had reestablished after
<br />only 4 years following rewatering (Jones and Stokes Asso-
<br />ciates, Inc., and Trihey Associates, persona] communica-
<br />tion). Along these recovering streams, willow and cotton-
<br />wood seedling densities were often >50 m'- with annual
<br />growth rates of 0.6 to 1S m high (B. Kauffman and P.. Besch-
<br />ta, Oregon State University, personal communication).
<br />i~o~~; vegetation establishment is beginning to intiuence
<br />channel diversity through the creation of narrower chan-
<br />nels, bank undercuts, and pools. In contrast, while sec-er.:
<br />million dollar; has been spe~;t or. en,ineern manipt;_ati~~~-.-
<br />S~~c;a! Iss.e o~, ti~`~iefersned Restora_tio~
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